1. Technical Field
The present disclosure relates to a differential, and, more particularly, to a locking differential in which each side gear is independently locked to the differential casing so that torque is not transmitted through the pinion gears when the differential is locked.
2. Description of the Related Art
Differential gear sets are employed to allow a pair of driven wheels connected to aligned axle half shafts to be driven at differential speeds. For example, when a vehicle turns the outside wheel must rotate faster than the inside wheel. To allow for such cornering while maintaining tires in consistent rolling contact with the ground, the differential gear set allows one of the output half shafts to rotate at a different speed as compared to the other output half shaft.
In some circumstances, it can be desirable to lock the differential such that two driven half shafts do not allow for differential rotational speeds of their wheel. For example, if the vehicle loses sure footing such that one of the two wheels receives little resistance to its rotation while the other wheel has normal or high resistance, nearly all rotational input to the differential will be transferred to the low-traction wheel, causing it to spin freely over the low-traction surface while the high-traction wheel receives no rotational input. This allocation of rotational input to the low-traction wheel can prevent the vehicle from moving in response to torque input to the differential. However, if the differential is locked, the wheels are constrained to rotate at the same speed and the higher-traction wheel can use its torque to move the vehicle.
Existing locking differentials utilize various structures to lock one of the side gears to the differential casing. With one of the side gears locked to the differential casing, torque input to the differential casing is transferred via the locked side gear to the corresponding axle half shaft. Further, because one of the side gears is locked to the differential casing, rotation of the pinion gears is disallowed so that torque transmitted to the differential casing is further transmitted through the pinion gears to the non-locked side gear so that both side gears (and the associated axle half shafts) rotate at the same speed as the differential casing.
Existing “limited slip” type differentials utilize clutch arrangements in engagement with one or both of the side gears and the differential casing. The clutch(es) can be actuated to provide a high frictional resistance to rotation of the side gear(s) relative to the differential case, thereby transferring some torque to a higher-traction wheel when the clutches are actuated. U.S. Pat. No. 5,531,653 shows one such limited slip differential design.
Yet another differential design, such as the Detroit Locker® differentials available from Eaton Corporation of Cleveland, Ohio utilize multi-piece differential casing structures that normally transmit torque to both driven wheels but allow differential rotation when a threshold differential torque is applied to the wheels. U.S. Pat. No. 6,681,654 shows a locked differential in which axle couplers are drivingly engaged with axle drivers by a plurality of mutually engaging teeth formed on respective faces of the couplers and drivers. A camming interrelationship between the two drivers operates to pull the driver inward to clear the driving teeth from the axle coupler when differential rotation occurs.